Power Generation Engineering And Services Company

1
Power Generation Engineering And Services Company
Department of Civil Engineering Structural
Design Central Group
Modeling of Composite Steel Floors Using GT STRUDL
A Presentation Submitted to GT STRUDL Users
Group 24th Annual Meeting Training Seminar To
Address Application of GT STRUDL for Structural
Analysis of composite steel section
February, 2012
2
Power Generation Engineering And Services Company
PGESCo.

1. PGESCo stands for (Power Generation Engineering
   Services Company)
2. Established in 1994
3. Located in Cairo, Egypt
4. Focused on EPCM (Engineering, Procurement,
   Construction and Management)
5. Produced more than 20,000MW

3
Rendered View of a Combined Cycle Power Plant
CTG / STG
3
CTG ( Combustion Turbine Generator)/ STG (Steam
turbine Generator)
4
Structures in power plants where composite slabs
are used

1. Steam Turbine Generator STG Building.
2. Combustion Turbine Generator CTG Building.
3. Control building.
4. Electrical building.
5. Circulating Water Electrical Building CWEB.

5
Control building during construction
5
6
Control building model using Gtstrudl

• Model include
• structural steel
• upper part and the
• concrete lower part
• (Walls and Slab)
• -Concrete slab
• is represented by big
• horizontal X brace to
• simulate rigid
• diaphragm action. The
• purpose of this study is
• how to model the slab
• as a diaphragm and a
• support for gravity
• loads.

6
7
Models used to simulate Composite Steel Floor
1- Full model 2- Springs were used to replace
beams to control deflection 3- Plate
elements were deleted at corners only. 4-
Plate elements on the girders were deleted
to insure floor was not spanning between
girders. 5- Element has one direction 6-
Sequential analysis 7- Rigid element between
beam slab 8- Master Slave 9- Eccentricity
between the centerline of plate and steel
beams.
7
8
Criteria for the normally used design model.

• Bending moments in the slab, approach
  approximate values
• obtained using continuous beam analysis results
  (confirm one
• way action),
• Bending moments in beams (confirm transverse
  beams support
• of the concrete slab)
• Bending moment in the Girders (Confirm Girders
  support of the
• transverse beams).
• Lateral deflection ( Confirm rigid diaphragm
  action by the
• concrete slab)
• The above 4 limits will be compared with a
  MANUAL
• calculation
• A simpler structure than the control building
  will be used
• for this case study.

8
9
Simple structure

• Slab thickness 200mm
• Gravity Load 1.0 metric tons/m2 (200psf)
• Lateral Load 10.0 metric tons (22.0 kips)
• Hinged supports at column bases.

9
10
Manual Calculation
Girder
Column
Filler beam
10
11
Manual Calculation

• For Concrete Slab-

11
12
Manual Calculation

• For steel filler beams-
• The steel (filler) beams behave
• simply supported on steel girders.
• Steel beam span (L) 10.0 meters.
• Beam uniform load (w) slab
• uniform load spacing
• 12 2.0 t/m
• Maximum bending moment
• (M)2102/8 25 m.t (180.8Kip.ft)
• Maximum deflection
• (?) 5(2(1000)4/(384210035088) 3.53
  cm 35.3 mm (1.39in)
• Reaction 210/210ton (22.04Kip)

12
13
Manual Calculation

• For steel girders-
• The steel girders behave simply
• supported on steel columns.
• Steel beam span (L) 10.0 meters.
• Steel girder loads are the reaction of
• filler beams
• Maximum bending moment
• M0.6101060 m.t (433.9 kip.ft)
• Maximum deflection (?) (0.06310(1000)3/(210
  056191) 5.34 cm 53.4 mm (2.1in)
• Reaction410/220 ton (44.1 kip.ft)

13
14
1-Full model used

• 10m X 10m X 6m high structure.
• Braced in one direction frame
• action in the other.
• Columns W10X33, and vertical
• brace WT5X11
• Girder size of W24X55, and
• transverse beams size of W21X44
• Slab thickness 200mm supported by
• the steel filler beams.
• Gravity Load 1.0 metric tons/m2 (200psf)
• Lateral Load 10.0 metric tons (22.0 kips)
• Hinged supports at column bases.

14
15
1-Full model used
Bending in filler beams girders uniformly loaded
15
16
1-Full model used

• Bending in slab (Neg. mom. 0.0)
• One way action does NOT exist

16
17
1-Full model used
Displacement at joints in mm under Load 1 Seems
like slab is supporting the filler beams. Hand
Calculation shows filler beam max deflection
35.3 mm (1.39 in)
17
18
1-Full model used

• GT results are quite different from the results
  obtained by the
• manual calculation because of the combined
  action of the slab
• and the steel beams.
• Each of the upcoming trials has its own
  perspective in choosing
• the methodology to represent the composite
  action of floor
• beams.
• Each model presented a different set of problems
  simulating
• composite action.
• A comparison of the results will be made with
  manual
• calculation. The results will be evaluated to
  understand the
• reasons for differences of the results from
  those of manual
• calculations.

18
19
2-Springs used to control deflection

• Solve the beam manually for uniform load W
  obtained by
• multiplying the area uniform load by beam
  spacing
• Calculate the deflection _at_ 0.5m intervals(0.5m
  X 0.5m
• Plate elements)
• Multiply the uniform load by 0.5m to get
  concentrated load
• Divide the concentrated load by the deflection
• calculated manually at this point to get
  stiffness

19
20
2-Springs used to control deflection

• This stiffness used represents the steel beam.
• In the model the steel beams are replaced by the
  calculated
• spring constants.
• This model cannot be used simply because the
  added springs generate vertical reactions that
  are not transmitted to the columns which
  generate lower reaction loads at the columns.

20
21
3-Delete plates at corners only

• Delete elements at the corners to prevent the
  slab from being directly supported by the columns

21
22
3-Delete plates at corners only

• Bending moment
• in the steel beam

22
23
3-Delete plates at corners only

• Bending moment in the
• slab

23
24
4- Delete plate elements on the girders

• Delete the plate elements that rest on the
• girder to force the slab to
• transfer the load to the
• beams then to the girders
• then to the columns

24
25
4- Delete plate elements on the girders

• Bending moment
• in the steel beams

25
26
4- Delete plate elements on the girders

• Bending moment in the
• slab

26
27
4- Delete plate elements on the girders

• Vertical displacement

27
28
5- Element has one direction of
distribution

• PSRR element type are used in modeling
• The problem that the PSRR elements do not
• permit the consideration of bending stiffness
• analysis nor the dynamic analysis

28
29
6-Sequential analysis

• A thought was discussed that the sequential
  analysis will get GTS to differentiate between
  the stage when the concrete is wet and the next
  stage when the concrete hardens.
• This approach was not what was thought to be and
  hence, it was abandoned.

29
30
7- Rigid elements between beam and slab

• This modeling technique did not
• produce a good representation
• of the bending moment which
• can not be explained.

30
31
8- Use of Master and Slave Joints

• This also did not produce a good
• representation of the bending moment.

31
32
9- Eccentricity

• Eccentric between the steel member and
• the concrete plate elements

32
33
9- Eccentricity

• Weird Bending moment diagram which had no
  explanation.

33
34
9- Eccentricity

• Bending in
• the slab

34
35
Models used to simulate hand calc till now
1-Full model 2-Springs were used to replace beams
to control deflection 3-Plate elements were
deleted at corners only. 4-Plate elements on
the girders were deleted to insure floor was
not spanning between girders. 5- Element has
one direction 6- Sequential analysis 7- Rigid
element between beam slab 8- Master
Slave 9-Eccentricity between the centerline of
plate and steel beams.
35
36
What to do next???

• None of the above modeling techniques produced a
  good representation of the approximate manual
  approach. So a combination of the above modeling
  techniques will be tried to reach a reasonable
  representation of the structure with some
  modification
• It was suggested to use a combination of the
  eccentric modeling
• approach together with the deleted elements at
  the corners for
• Easy to model applicable for every day work
• Actual representation of the differences between
  the steel
• beam CL and the concrete slab CL.
• The modification will be by varying one of the
  following
• parameters
• Thickness of the slab
• Young's Modules of the concrete slab

36
37
Variation in Thickness for the slab
37
38
Variation in Thickness for the slab
38
39
Variation in E for concrete
39
40
Variation in E for concrete
40
41
Variation in E for concrete

• Bending moment
• in the steel beam
• Case 0.25 E

41
42
Variation in E for concrete

• Bending moment
• in the slab
• Case 0.25 E

42
43
Variation in E for concrete

• Lateral difflection in Z
• direction
• (Braced Dir.)

43
44
Variation in E for concrete

• Lateral deflection in X
• direction
• (Moment frame dir.)

44
45
Verification Other Software
Comparing results to those obtained by using
another software an other program with a
composite beam module built in
45
46
Verification Other software
46
47
Conclusion

• Using the Eccentric model with the deleted shell
  element at the corner with a reduction in the E
  of the concrete slab, produces results in
  agreement with the manual calculations. The
  following table summarize these results.

47
48
Questions and Discussion